Vertical laminar-flow clean room of flexible design

ABSTRACT

A vertical laminar-flow clean room is contained within a bounding enclosure which is substantially airtight. The clean room floor is raised and has apertures therein. The floor and the bottom of the bounding enclosure form an air-receiving plenum. A dropped ceiling is formed of an assembly of blower-hood-filter units, with the space directly above the dropped ceiling constituting an air-supply plenum. Air return plenums are contained entirely within the bounding enclosure and preferably incorporate prefilters and air-conditioning equipment, and the air return plenums connect the air-receiving plenum to the airsupply plenum. The blower-hood-filter units and air return plenums are all of a similar size, in order to facilitate a modular-type of construction and flexibility of design.

0 United States Patent [151 3,638,404 Moll et al. Feb. 1, 1972 [54]VERTICAL LAMINAR-FLOW CLEAN OTHER PUBLICATIONS ROOM 0F FLEXIBLE DESIGNAustin P. R. 14 Types of Clean Rooms are Available for Selec- [72]Inventors: Charles J. Moll; William C. Anderson, tion" All EngineeringPages sand 1916b I968 both of Grand Rapids, Mich. P E F k w L rimaryxaminerran utter [73] Assrgnee: Westinghouse Electric Corporation, Pitt-Asst-8mm Examiner aemaxd Nozick Sburgh' Attorney-A. T. Stratton, W. D.Palmer and D. S. Buleza [22] Filed: Sept. 30, 1969 [57] ABSTRACT [21]Appl. No.: 862,430

A vertical laminar-flow clean room is contained within a boundingenclosure which is substantially airtight. Theclean [52] U.S. Cl...55/473, 55/484, 98/40 D mom floor is raised and has apertures thereinThe floor and [51] lnt.Cl. ..B01d 31/700 the bottom of the boundingenclosure form an air receiving ofSearch 3, plenum. A pp ceiling isformed of an of 55/4 8 I D blower-hood-filter units, with the spacedirectly above the dropped ceiling constituting an air-supply plenum.Air return [56] References cued plenums are contained entirely withinthe bounding enclosure UNITED STATES PATENTS and preferably incorporateprefilters and air-conditioning equipment, and the air return plenumsconnect the air-receiv- Taylor ing plenum to the aipsupply plenum Theblowe -hood-fi|ter 3,158,457 1 H1964 whlffleld units and air returnplenums are all of a similar size, in order to 3,280,540 10/1966 Soltrs..55/484 f ilit t a modul-amype f construction and fl ibilit f 3,284,14811/ 1966 Ramniceanu.... ..98/1l5 design 3,353,472 11/1967 Lee et al.....98/40 D 3,356,006 12/ 1 967 Scott ..55/470 6 Claims, 9 DrawingFigures PATENTEU FEB 1 I972 SHEET 6 BF 6 FIG. 9

VERTICAL LAMINAR-FLOW CLEAN ROOM OF FLEXIBLE DESIGN BACKGROUND OF THEINVENTION So-called clean rooms are now well known and are used tofabricate precision electronic and mechanical equipment, as well asother applications which require ultraclean atmosphcres, such ashospital operating rooms. The basic function of a clean room is toremove from the atmosphere substantially all particulate matter whichmight contaminate the products assembled in the room.

As a general rule, the best performing clean rooms for removing allpossible particulate matter are of a design which is known in the art asvertical laminar flow, and such a clean room is described in U.S. Pat.No. 3,158,457, dated Nov. 24, I964. In the general design of such cleanrooms, the ceiling normally comprises so-called high-efficiencyparticulate air (HEPA) filters, which are now well known in the cleanroom art. Such HEPA superinterception filters have a 99.97 percent to99.999 percent efficiency for 0.3-micron particles, as measured with adioctyl phthalate (DOP) test. In the operation of most clean rooms, airpasses from an overhead plenum above the filters, through the filters,vertically downward through the clean room, through an apertured floorin the clean room into an air-receiving plenum, and thence through avery large fan and duct system and back to the'air-supply plenum whichis located above the superinterception filters. In such a system, thefans for circulating the air are of very large size and are normallylocated externally of the bounding enclosure for the clean-room. Inaddition, the duct work which connects the airreceiving plenum below theapertured floor and the supply plenum above the filtered ceiling isnormally located exteriorly of the clean room proper. The necessity forthe very large fans the the location of the connecting duct works havelimited the flexibility of design for such clean rooms, particularly forapplications where equipments are to be moved within the clean roomafter initial installation or expansion of the facility is requircd.

It is the general object of the present invention to provide a verticallaminar-flow clean room which is of flexible design and can be readilyaltered.

It is another object of the invention to provide a vertical laminar-flowclean room which is constructed on a modular basis in order tofacilitate standardization of parts and ease of construction.

It is a further object to provide a vertical laminar-flow clean roomwherein all elements which comprise the clean room are located withinthe bounding enclosure, in order to facilitate maintaining the cleanroom substantially airtight.

The foregoing objects of the invention, and other objects will becomeapparent as the description proceeds, are achieved by providing avertical laminar-flow clean room which comprises a bounding enclosureformed by sidewalls, a top wall and a bottom wall, with the enclosurebeing substantially airtight except as to permit necessary personnelingress and egress and to provide for makeup air which may be introducedin a controlled fashion. A raised floor which has apertures therein ispositioned over the bottom wall, with the space between the raised floorand the enclosure bottom wall constituting an air-receiving plenum. Anair-moving system is supported beneath the top wall of the boundingenclosure and comprises a plurality of blower-hood-filter assemblies,each of which comprises a hood portion having an open airinlet and anair outlet portion terminating in a high-efficiency (HEPA) filter. Thespace between the air-moving system and the top wall of the boundingenclosure constitutes an air-supply plenum. At least one verticallydisposed air return plenum, which is located entirely within theconfines of the bounding enclosure, connects the air-receiving plenumand the airsupply in an airtight fashion. Prefilters are desirablypositioned within the air return plenum. The lateral dimensions of eachair return plenum and each blower-hood-filter assembly are identical inorder to facilitate the use of a modular-type of construction.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention, reference should be made to the accompanying drawingswherein:

FIG. I is an isometric, diagrammatic view, partly broken away, showingthe general positioning of the components which comprise the presentclean room;

FIG. 2 is a perspective view ofa portion of the interior of the cleanroom of the present invention showing a portion of the aperture raisedfloor, a portion of the false ceiling, and air return plenums whichcontain air-conditioning equipment as well as prefilters;

FIG. 3 is an elevational view, partly in section, of a blowerhood-filterassembly component ofthe present invention;

FIG. 4 is an end view of the assembly as shown in FIG. 3;

FIG. 5 is a plan view of the assembly as shown in FIG. 3;

FIG. 6 is a bottom view of the assembly as shown in FIG. 3;

FIG. 7 is a fragmentary elevational view, shown partly in section, of aportion of a clean room of the present invention illustrating twoblower-hood-filter assemblies and an adjacent air return plenum;

FIG. 8 is a fragmentary elevation, partly in section, illustrating aside view of the air return plenum as shown in FIG. 7;

FIG. 9 is a fragmentary view of a portion of a ceiling for a clean roomconstructed in accordance within the present invention wherein two airreturn plenums are positioned adjacent one another and twoblower-hood-filter assemblies are replaced by airtight filler members,such as might be used where equipment is to be placed directlytherebeneath.

DESCRIPTION OF PREFERRED EMBODIMENTS With specific reference to the formof the invention shown in the drawings, in FIG. I is shown a verticallaminar-flow clean room 10 which comprises a bounding enclosure formedby sidewalls 12, a top wall 14 and a bottom wall 16, and the boundingenclosure is substantially airtight except for ingress and egress ofpersonnel and material and to provide for makeup air which may beintroduced therein in a controlled fashion, such as through theconventional air-conditioning equipment.

There is positioned within the bounding enclosure a raised floor 18which constitutes the floor for the clean room and which has apertures20 therein in order to permit air to flow therethrough. The raised floorl8 abuts the sidewalls 12 at its periphery and is supported on andpositioned over the bottom wall 16 by pedestals 22 and such floors aregenerally known in the art. The space between the raised floor 18 andthe bottom wall 16 constitutes an air-receiving plenum 24.

Beneath the top wall 14 is positioned an air-moving filter system 26 theperiphery of which abuts the sidewalls l2 and having a bottom surface 28which constitutes the ceiling for the clean room, and the air-movingfilter system 26 will be described in greater detail hereinafter. Thespace between the air-moving filter system 26 and the top wall I4comprises an air supply plenum 30. The only passage for air directlyfrom the air-supply plenum 30 and into the clean room proper is throughthe air-moving filter system 26. At least one vertically disposed airreturn plenum 32 is located within the confines of the boundingenclosure and connects the air-receiving plenum 24 and the air-supplyplenum 30 in an airtight fashion.

The general layout of the clean room is shown in perspective view inFIG. 2 wherein the raised floor 18 comprises a plurality of individualsquare or rectangular units which have apertures therein, and theceiling as viewed from the clean room comprises a plurality of HEPAfilters 34, along with the associated lighting units 36. The air returnplenums 32 can have positioned on the exterior thereof the necessary temperature and humidity controls 38 for the air-conditioning apparatuscontained therein, as well as fan controls for the airmoving filtersystem.

The air-moving filter system 26 comprises a plurality of blower-hoodfilter assemblies 40, as shown in FIGS. 3,4,5 and 6, which can besupported from the top wall 14 or supported on an inverted T-bar grid.Each of the assemblies comprises a hood unit 42 and associated blowerhousing 44 which has an open air inlet portion 46. The air outletportion 48 of the hood 42 terminates in the superinterception (HEPA)filter combination 34. The motor unit 50 is suitably vibration mountedand the blower housing portion 44 is connected to the rest of the hoodby a suitable vibration damping connection 52. The hood 42 is designedto insure uniform air distribution.

As viewed from the bottom, and as shown in FIG. 6, which illustrates theportion of the assembly 40 that is viewed from the clean room proper,each assembly comprises five 2-foot by 4-foot combination HEPA filters34 sealed together at their edges in an airtight fashion to form oneassembly unit measuring 4 feet by 10 feet. Along either side of theassembled filters are affixed the fluorescent lamp fixtures 36 whichcomprise the usual troffers together with the associated refractor unitsfor such fixtures and the bottom surface of the assemblies 40 comprisethe ceiling 28 for the clean room. The entire blowerhood-filter assembly40 measures 5 feet by feet in overall lateral dimensions, as measured atthat portion thereof which comprises a part of the ceiling 28 of theclean room, and when mounted in a clean room, as shown in FIG. 1, eachof these assemblies comprises a modular unit and is affixed to adjacentassemblies in an airtight fashion. Between the light fixtures 36 areprovided unused panels 54 which can be adapted to receive sprinklerheads, paging systems, emergency lights, or other auxiliary systems.

In FIGS. 7 and 8 are shown two blower-hood-filter assemblies 40 and anadjacent air return plenum 32. In this plenum 32 are mounted prefilterunits 56 which operate with an efficiency of up to 85 percent. Alsomounted within the air return plenum 32 is conventional air conditioningequipment 58 which may be used for heating, humidity control and/orcooling. The controls for such equipment, as well as the blower units,are readily mounted on the exterior surface of the return plenum 32,generally as illustrated in FIG. 2.

In FIG. 9 is shown a modified ceiling plan for a clean room whichillustrates the flexibility of the present design. The air returnplenums 32 as shown here are placed in side-by-side relationship and areof the same lateral dimensions as the assemblies 40 to provide a modularconstruction. If desired, any of the assemblies 40 may be replaced by anairtight filler unit 60 which provides no air-moving or -filteringfunction. Such a filler unit can be readily installed directly abovelarge apparatus, in order that the airflow through the room ismaintained as nearly vertical, from ceiling to floor, as possible. Also,if a room is desired to have only a limited clean" area withsupplemental areas of storage, for example, surrounding the clean area,a large number of the filler units 60 can be used over the supplementalareas. These filler units can be replaced thereafter, if desired, withthe blower-hood-filter assemblies 40 to upgrade the overall room.

The present system is extremely flexible in design inasmuch as thelateral dimensions of the air return plenums or ducts 32 are the same asthose of the modular blower-hood-filter assemblies 40 so that thelocation of the air return plenums 32 can be individually changed asdesired, even after the room is completed and in operation. This permitsmanufacturing apparatus to be readily shifted from one location toanother with a minimum of inconvenience.

In the construction of the preferred embodiment as describedhereinbefore, for each air return plenum 32 there should be providedfrom about eight to about 14 of the blower-hood-flltcr assemblies 40, inorder to ensure proper performance. The preferred ratio is one airrcturn plenum 32 for every l0 blower-hood-filter assemblies 40. The fansfor each of the assemblies 40 can be varied in speed in order tocarefully control the flow of air in various parts of the room.

Briefly summarizing the operation of the clean room, air passes throughthe H EPA filters 34 and downward through the clean room in a verticalfashion, through thev apertures in the raised floor 18 and into theair-receiving plenum 24. From there the air passes upward through thevertically disposed air return plenums 32, the air is conditioned asrequired, and then passed through the prefilters 56 into the air supplyplenum 30. The air is then passed through the air inlet 46 of theassembly 40, through the air outlet 48 and again through the HEPAfilters 34.

In the preferred embodiment as described hereinbefore, both theprefilter units 56 and the air-conditioning equipment 58 are located inthe air return plenums 32. As an alternative embodiment, the prefilterunits could be located directly beneath the apertured raised floor.Also, the air-conditioning equipment could be positioned either in theair'receiving plenum 24 or the air-supply plenum 30. With such aconstruction, the air return plenums 32 could be changed from locationto location even more readily, in order to facilitate design changes inan established clean room. Such facility of design changes is madepossible by the modular construction wherein the modules 40 whichcomprise the ceiling are of the same lateral dimensions as the airreturn plenums 32.

The present clean room has many operational advantages. For example,each blower-hood-filter assembly 40 is provided with its own small motorand fan, and the clean room does not require the massive motors and fansas have been needed to operate most clean rooms of the prior art. Theair-supply plenum 30 is maintained at a pressure which is less than thepressure in the clean room proper so that any sealing faults will notconstitute paths for leakage of any dirt. Also, each air return plenum32 is located in the immediate area it serves and handles only the airfor a relatively small group of modules 40, thereby eliminating longpassages for return air movement and reducing plenum heights over theroom. If one of the small fans of the present clean room fails, theoperation of the room is substantially unimpaired, in contrast to thefailure of a large blower unit. In addition, less gross floor area isrequired by the clean room of this invention because of the eliminationof a separated equipment room, large fans, and ducts, etc., positionedoutside the clean room proper. This also permits the clean room to beexpanded readily, since there is no need to change the location ofacentral equipment room. Zoned temperature and humidity control is alsofacilitated by the individual control which is made possible by the useof the modular air return plenums 32, which have the local controlspositioned in the zone desired to be controlled.

It will be recognized that the objects of the invention have beenachieved by providing a clean room which is very flexible in design andwhich is readily fabricated on a modular basis. The room is veryefficient in operation and airflow is readily controlled.

We claim:

1. A vertical laminar-flow clean room comprising:

a. a bounding enclosure formed by sidewalls, a top wall, and

a bottom wall, said bounding enclosure being substantially airtightexcept as to permit necessary personnel and material ingress and egressand to provide for makeup air which may be introduced therein in acontrolled fashion;

b. a raised floor having a periphery which abuts said sidewalls andwhich constitutes the floor for said clean room, said raised floorhaving apertures therein to permit airflow therethrough, said raisedfloor positioned over said bottom wall, and the space between saidraised floor and said bottom wall constituting an air-receiving plenum;

c. an air-moving filter system having a periphery which abuts saidsidewalls and a bottom surface which constitutes the ceiling for saidclean room, said air-moving filter system supported beneath said topwall and comprising a plurality of blower-hood-filtcr assemblies, saidblower-hood-filter assemblies each comprising a hood unit having an openair inlet portion and an air outlet portion terminating inhigh-efficiency air filter means which comprises a part of said ceiling,with the overall lateral dimensions of each said blower-hood-filterassembly as measured at that portion thereof which comprises a part ofsaid ceiling being the same, and a blower unit operable to move air fromsaid open air inlet portion and to and through said high-efficiency airfilter means, the bottom surface of said air'moving system as viewedfrom said raised floor comprising a plurality of said air filter means,an air-supply plenum formed by the space between said air-moving systemand said top wall, and the only passage for air directly from saidair-supply plenum and into said clean room being through saidblower-hood-filter assemblies; and

d. vertically disposed air return plenum duct means located entirelywithin the confines of said bounding enclosure and connecting saidair-receiving plenum and said airsupply plenum in an airtight fashion,and each said air return plenum duct means having the same overalllateral dimensions as said overall lateral dimensions of each saidblower-hood-filter assembly in order to be readily assembled therewithand interchangeable therewith.

2. The clean room as specified in claim 1, wherein air-conditioningequipment is mounted within said air return plenum duet means.

3. The clean room as specified in claim 2, wherein controls for saidair-conditioning equipment and controls for the blower units of saidblower-hood-filter assemblies are located on the exterior lateralsurface of said air return plenum duct means.

4. The clean room as specified in claim I, wherein prefilter means ismounted within said air-return plenum duct means.

5. The clean room as specified in claim 4, wherein each said

1. A vertical laminar-flow clean room comprising: a. a boundingenclosure formed by sidewalls, a top wall, and a bottom wall, saidbounding enclosure being substantially airtight except as to permitnecessary personnel and material ingress and egress and to provide formakeup air which may be introduced therein in a controlled fashion; b. araised floor having a periphery which abuts said sidewalls and whichconstitutes the floor for said clean room, said raised floor havingapertures therein to permit airflow therethrough, said raised floorpositioned over said bottom wall, and the space between said raisedfloor and said bottom wall constituting an air-receiving plenum; c. anair-moving filter system having a periphery which abuts said sidewallsand a bottom surface which constitutes the ceiling for said clean room,said air-moving filter system supported beneath said top wall andcomprising a plurality of blower-hood-filter assemblies, saidblower-hood-filter assemblies each comprising a hood unit having an openair inlet portion and an air outlet portion terminating inhighefficiency air filter means which comprises a part of said ceiling,with the overall lateral dimensions of each said blower-hood-filterassembly as measured at that portion thereof which comprises a part ofsaid ceiling being the same, and a blower unit operable to move air fromsaid open air inlet portion and to and through said high-efficiency airfilter means, the bottom surface of said air-moving system as viewedfrom said raised floor comprising a plurality of said air filter means,an air-supply plenum formed by the space between said air-moving systemand said top wall, and the only passage for air directly from saidair-supply plenum and into said clean room being through saidblower-hood-filter assemblies; and d. vertically disposed air returnplenum duct means located entirely within the confines of said boundingenclosure and connecting said air-receiving plenum and said air-supplyplenum in an airtight fashion, and each said air return plenum ductmeans having the same overall lateral dimensions as said overall lateraldimensions of each said blower-hood-filter assembly in order to bereadily assembled therewith and interchangeable therewith.
 2. The cleanroom as specified in claim 1, wherein air-conditioning equipment ismounted within said air return plenum duct means.
 3. The clean room asspecified in claim 2, wherein controls for said air-conditioningequipment and controls for the blower units of said blower-hood-filterassemblies are located on the exterior lateral surface of said airreturn plenum duct means.
 4. The clean room as specified in claim 1,wherein prefilter means is mounted within said air-return plenum ductmeans.
 5. The clean room as specified in claim 4, wherein each said airreturn plenum duct means is located in the immediate area it is intendedto serve, and for each said air return plenum duct means there areprovided from about eight to 14 of said blower-hood-filter assembliesthereby to eliminate long passages for return air movement.
 6. The cleanroom as specified in claim 5, wherein for each air return plenum means,there are provided about 10 of said blower-hood-filter assemblies.